The present invention relates to a movable body driving device for automatically opening and closing a door of a vehicle such as a train.
For example, a technique using a linear motor is commonly known as a background-art technique of applying a movable body driving device to a drive device for opening and closing a vehicle door. When such a linear motor used for a vehicle is a movable coil type driving device, the length of a stator is structurally equal to the sum of the length of a door stroke and the length of a moving member. The length of the door stroke is generally in a range from 600 mm to 900 mm.
There is, however, a problem that the linear motor becomes expensive because the linear motor requires a large quantity of rare-earth permanent magnets as permanent magnets in addition to increase in device size.
In order to achieve both reduction in device size and reduction in cost, a movable body driving device including a motor equipped with an encoder for controlling the velocity and direction of rotation of the motor, a pinion driven to rotate by the motor, and upper and lower racks driven to move linearly by the pinion has been therefore known as a technique according to the background art (e.g. see JP-A-2007-297796).
In the movable body driving device, when the motor rotates either forward or backward, the pinion fixed to a motor shaft rotates either forward or backward accordingly so that the upper and lower racks move laterally in the reverse directions.
One of the left and right doors is attached to the upper rack through an upper rack connection and door hangers while the other of the left and right doors is attached to the lower rack through a lower rack connection and door hangers. The left and right doors are opened and closed when the upper and lower racks move laterally in the directions reverse to each other.
Only one pinion is disposed in the center of the movable body driving device. As a drive method for opening and closing a door, the pinion disposed in the center of the movable body driving device is paired exclusively with either one of the upper and lower racks so as to correspondingly drive either one of the left and right doors.
FIGS. 2A and 2B are views showing an example of one door to be opened/closed for easy understanding of the structure and operating state of the movable body driving device according to the background art, which operates so that the pinion is paired exclusively with either one of the racks. FIG. 2A shows a state when the door 1 is in a closed position 2, and FIG. 2B shows a state when the door 1 is in an open position.
As shown in FIGS. 2A and 2B, a pinion 4 fixed to one end of a power shaft of a motor 3 is housed, together with a rack 5 engaging the pinion 4, in a rack and pinion housing 6.
The door 1 is connected to the rack 5 through a connection 7 and two door hangers 8. Two guide rollers 12 are attached to each of the door hangers 8 which are connected to opposite end portions of the door 1, respectively. The two guide rollers 12 are loosely fitted into a rail groove 11 formed in a lower end portion of a door rail 9 so that the two guide rollers 12 guide the opening/closing movement of the door 1.
One adjusting roller 13 is disposed between the two guide rollers 12 in order to suppress rattling noise generated during the opening/closing operation of the door 1 due to play of the two guide rollers 12 with respect to the rail groove 11.
In order to prevent the two guide rollers 12 and the adjusting roller 13 in the door hanger 8 connected to a right end portion of the door 1 in a close position from dropping out of the rail groove 11, a right end portion of the rack and pinion housing 6 is extended to the same position as a right end portion 14 of the door 1 in a close position. Incidentally, a cushioning member 15 made of a rubber member or the like is attached to the right end portion 14 of the door 1 in order to prevent an accident during the closing of the door.
In the example shown in FIGS. 2A and 2B, the position of the pinion 4, i.e. the position of the motor 3 where the pinion 4 is fixed to one end of the power shaft of the motor 3 is determined to be a position at a distance A from a left end portion 16 of the door 1 when the door 1 is closed, because of the circumstances where the whole device is attached.
Accordingly, a left end portion of the rack 5 connected to the door 1 is always located at a distance A+d left from the left end portion 16 of the door 1. The distance d is a length of play provided on the left side from the center position of the pinion 4 so that the pinion 4 can engage the rack 5 stably when the door 1 is in a close position shown in FIG. 2A.
In this configuration, when the pinion 4 rotates clockwise in FIG. 2A from the close position shown in FIG. 2A, the rack 5 moves left so that the door 1 connected to the rack 5 through the connection 7 and the two door hangers 8 moves to the open position shown in FIG. 2B. In this manner, the door 1 is opened.
On this occasion, the left end portion of the rack 5 is located at the distance A+d left from the left end portion 16 of the door 1 as described above. Accordingly, the length of the rack and pinion housing 6 is equal to a length from a right end portion corresponding to the right end portion 14 of the door 1 in the close position as shown in FIG. 2A to a left end portion located at a distance A+d+e (obtained by adding up the distance A, the distance d and the length e of play) from the left end portion of the door 1 in the open position shown in FIG. 2B.
As described above, the rack and pinion mechanism in the vehicle door driving device according to the background art structurally requires a length corresponding to left and right door opening/closing movement distances from the center position of the pinion. Each of the left and right door opening/closing movement distances is generally in a range of from 600 mm to 900 mm.
That is, in the rack and pinion structure according to the background art, the total length of the rack and pinion housing 6, i.e. the total length of the device as a whole, is determined based on the position of the pinion because the pinion is paired exclusively with either one of the racks. In other words, the total length of the device depends on the position of the pinion.
When the vehicle door driving device according to the background art is applied to a door driving device having a motor directly attached to a pinion, the position of the motor is equal to the position of the pinion. Since the position where the motor is attached to the vehicle is limited, the total length of the device determined based on the position of the pinion may become long because of the position where the motor is attached. In this case, there arises a problem that it is difficult to attach the device to the vehicle in accordance with the circumstances of the body of the vehicle.
Even if the position for arrangement of the pinion is shifted in order to avoid occurrence of such a problem, the problem cannot be solved because the pinion will excessively occupy a space for rigging the vehicle body in other respects.
In order to solve the problem, an object of the invention is to provide a movable body driving device whose total length can be fixed to be short.
Further objects and advantages of the invention will be apparent from the following description of the invention.